Unsupported browser (feature)

modules/RTC/RTCUtils.js

                     RTCBrowserType.isNWJS() ||
                     RTCBrowserType.isElectron() ||
                     RTCBrowserType.isReactNative()) {
+
                 this.peerconnection = webkitRTCPeerConnection;
                 var getUserMedia = navigator.webkitGetUserMedia.bind(navigator);
                 if (navigator.mediaDevices) {
             }
             // Detect IE/Safari
             else if (RTCBrowserType.isTemasysPluginUsed()) {
-
-                //AdapterJS.WebRTCPlugin.setLogLevel(
-                //    AdapterJS.WebRTCPlugin.PLUGIN_LOG_LEVELS.VERBOSE);
-                var self = this;
-                AdapterJS.webRTCReady(function () {
-
-                    self.peerconnection = RTCPeerConnection;
-                    self.getUserMedia = window.getUserMedia;
-                    self.enumerateDevices = enumerateDevicesThroughMediaStreamTrack;
-                    self.attachMediaStream = wrapAttachMediaStream(function (element, stream) {
+                const webRTCReadyCb = () => {
+                    this.peerconnection = RTCPeerConnection;
+                    this.getUserMedia = window.getUserMedia;
+                    this.enumerateDevices = enumerateDevicesThroughMediaStreamTrack;
+                    this.attachMediaStream = wrapAttachMediaStream((element, stream) => {
                         if (stream) {
                             if (stream.id === "dummyAudio"
                                     || stream.id === "dummyVideo") {
 
                         return attachMediaStream(element, stream);
                     });
-                    self.getStreamID = function (stream) {
-                        return SDPUtil.filter_special_chars(stream.label);
-                    };
+                    this.getStreamID
+                        = stream => SDPUtil.filter_special_chars(stream.label);
 
-                    onReady(options,
-                        self.getUserMediaWithConstraints.bind(self));
-                    resolve();
-                });
+                    onReady(
+                        options,
+                        this.getUserMediaWithConstraints.bind(this));
+                };
+                const webRTCReadyPromise
+                    = new Promise(resolve => AdapterJS.webRTCReady(resolve));
+
+                // Resolve or reject depending on whether the Temasys plugin is
+                // installed.
+                AdapterJS.WebRTCPlugin.isPluginInstalled(
+                    AdapterJS.WebRTCPlugin.pluginInfo.prefix,
+                    AdapterJS.WebRTCPlugin.pluginInfo.plugName,
+                    AdapterJS.WebRTCPlugin.pluginInfo.type,
+                    /* installed */ () => {
+                        webRTCReadyPromise.then(() => {
+                            webRTCReadyCb();
+                            resolve();
+                        });
+                    },
+                    /* not installed */ () => {
+                        const error
+                            = new Error('Temasys plugin is not installed');
+
+                        error.name = 'WEBRTC_NOT_READY';
+                        error.webRTCReadyPromise = webRTCReadyPromise;
+
+                        reject(error);
+                    });
             } else {
                 rejectWithWebRTCNotSupported(
                     'Browser does not appear to be WebRTC-capable',